This is a continuation-in-part of U.S. Pat. Application Serial No. 457,679 filed Jan. 13, 1983, now abandoned.
The invention relates to rotary surface grinders and more particularly to a mounting system for the abrasive segments of a segmented rotary grinding wheel. In a rotary surface grinder, the grinding wheel used to grind the surface of a workpiece or workpieces can be a solid continuous cylinder or a circular assembly of a number of abrasive segments of generally arcuate shape. The segments are assembled and interconnected so as to form a generally cylindrical grinding element leaving a flat end face which is mounted in the chuck of the grinder. Each segment must be tightly secured and held in place relative to other segments to maintain the flat end face and generally cylindrical configuration, no part of which should loosen or shift during grinding operations.
Typically, grinding wheels and segments are composed of bonded abrasive particles of aluminum oxide or silicon carbide ranging in hardness. In some instances, mixtures of those and similar abrasives are bonded together by conventional techniques such as vitrified silicate or resinoid bonds. To hold assembled segments together properly, it is necessary to use some form of clamping device and the segments would be subject to damage if the clamping members were in direct contact with the surfaces of the segments.
To avoid such damage and yet to securely mount the segments, it has been the practice to cement individual pads of an organic gasket material such as Vellumoid.RTM. onto the surfaces of each segment. These pads are generally four in number and serve to cushion the contact between the clamps and the segments as well as between the segments and the chuck. Although the basic protective cushioning function is served by the individual pads, other problems remain. For example, the cement joint between one or more of the pads and the segment is subject to failure during the grinding operation. Such failure of a cement joint frequently causes loss of proper mounting of the segment and production must stop to permit correction.
Another problem encountered with Vellumoid pads is their tendency to trap the coolant sludge around the clamp areas and that may interfere with precision grinding. One further problem is that as a segment is ground down to the point where the pads are located, the pads do not wear off in fine particles as the abrasive segment does, but rather, break off in relatively large pieces. These pieces can clog the coolant system, again causing interference with production because of machine down-time while corrective measures are taken.
A further serious disadvantage of the use of individually glued pads is the amount of time necessary for the gluing operation. The time-consuming gluing operation increases the cost of the abrasive segment. Another costly technique involves injection molding of a plastic casing around an abrasive element. Not only is this technique costly, but since the plastic casing virtually completely surrounds the element, the plastic casing material will be abraded away along with the abrasive material and the plastic oftentimes clogs the cooling system.
It is therefore an object of the present invention to eliminate the above-mentioned cost and other problems associated with the use of a plurality of individual pads which must be individually cemented in place.
It is a further object of the invention to provide cushioning between the clamp and the abrasive element without the need for a separate molding operation.
It is yet another object of the invention to provide cushioning between the segments and the clamps which can be applied to the abrasive segments at a high throughput rate.